How are we getting virus-free clones?

[orchidman77]

I need some hive knowledge!

I've had a virus-free clone of C. warscewiczii alba 'Firmin Lambeau' for awhile now and just ordered another cattleya hybrid that is almost certainly a virus-free clone from a CymMV positive mother plant. Looking online only got me to dissertations that took me far outside of what I know.

How is this possible? And, I have a note on the tag of my most recent purchase: "clone from DBE plant." Does anyone know what this means?

Many thanks! I'm going to contact the grower and see if I can learn anything from them, too.

[Orchid Whisperer]

Wondering how you know that the clones you have are virus-free? Have you tested them?

[Jmoney]

I believe rapidly-growing tissue may be virus-free since the virus has not had a chance to "catch up"; people can correct me but I think taking tissue from this clean area can lead to virus-free mericlones.

In a similar vein I have been having issues with virus positivity on catasetums that had previously tested negative (either by myself or in some cases the vendor). wondering if their rapid growth may lead to heterogeneity in virus presence and thus the false negatives.

[Ray]

The only way I can see a “virus-free” clone from a virused plant would be by getting extremely lucky and grabbing a few meristematic cells before they became infected, and I figure that is a hit-or-miss thing.

Do the meristem cells grow faster than viruses can replicate? I kind-of doubt it.

How can you know for sure the cells are virus-free, when the testing is destructive?

As far as “previously tested clean” plants ending up testing positive is concerned, we don’t know of the relative sensitivities of the two tests, the sample sizes, and it’s always possible that the virus was present but suppressed early on and cultural changes gave it a chance to flourish.

[Leafmite]

They may have done a few tries and got lucky with taking cells and cloning to get some plants that were virus free and it is possible that your plant is a clone of one of those.

The only way to guarantee a plant is completely virus-free is to use an electron microscope to test samples from different parts of the entire plant...which is expensive, time consuming and a stupid waste of resources.

[orchidman77]

Thanks, all.

I called and found out that "clone from DBE plant" was just a note from the grower - "DBE" are the initials of the person the plant came from. Grower confirmed the plant and mericlones are virus-free.

As for how to get virus-free clones: I only know this is a fairly new process. Several of the most reputable and well-known Cattleya-selling nurseries have all sold a few virus-free clones of very old vintage plants (species and hybrids alike), and I've seen notes of descriptions such as "scientists have engineered a new way to make virus-free clones of virused material." I was hoping someone had some answer to "how." From the little I could glean from abstracts online, it seems there is some outpacing of healthy, virus-free growth in vitro before the meristematic tissue differentiates.

[Jmoney]

interesting, thanks for the info. I had only heard through the grapevine about this but hadn't come across any actual literature. It has been reported that fast growth may outpace virus spread, so hence the ability to get "clean" plants. My other concern would be the "authenticity" if you are potentially dealing with small bits of clean tissue. (That is a problem to mericloning in general, hence the premium on original divisions).

[Ray]

Interesting, to say the least.

[orchidman77]

Interesting for sure, and I hope I'm not misrepresenting the process with ignorance. I'd love to learn more and will certainly update the thread if I do.

I think one huge benefit, if the process is indeed successful, is that we can "resurrect" virused - but spectacular - plants that are otherwise doomed to exist solely in a few collections given the disease. I'm so grateful to have a clone of the fabled 'Firmin Lambeau' as it's one of my most favorite species and a piece of living history.

[DirtyCoconuts]

my foggy memory recalls ES posting once about how viruses would not matter in a few years bc of something like this.

He is much smarter than i and he is the one i am poorly quoting so hopefully he will chime in.